This project proposes to examine the orientation and organizational structure of two phage T4-coded integral membrane proteins and their interaction with the deoxyribonucleotide synthetase complex. These proteins are formed by the DNA-delay genes, 39 and 52. Mutations of these genes decrease not only DNA replication but also deoxyribonucleotide synthesis. We are studying the nature of the interaction of the DNA-delay proteins with the membrane, with DNA and with peripheral proteins by cross-linking methods and in isolated membrane complexes.